This invention relates to housings in general and, in particular, to housings for static-sensitive electronic circuitry. CMOS electronic circuitry is particularly susceptible to damage by excessive voltages. Static electric discharges can have catastrophic effect on CMOS circuitry, and as such it is important to protect CMOS circuitry as well as other electronic circuitry from such static electric discharge.
CMOS circuitry is characterized by its low power and low voltage properties which make it highly desirable for use in battery operated portable electronic equipment such as radio paging receivers. In order to reduce the weight of such units, it is desirable to manufacture housings for pagers and similar equipment out of lightweight plastics. Such plastic housings do provide electro-static insulation. A problem can exist when it is necessary to extend metallic elements such as fasteners through the outer wall of the plastic housing to its interior. Such electrically conductive fasteners can provide a point for the buildup of static-electric charges and allow current flow to the interior of the housing where it can flow through air and damage CMOS circuitry.
While it is possible to utilize non-conductive fasteners, such fasteners generally do not have the same characteristic strength of metallic fasteners. In products such as pagers which are worn on or about the clothing of a person, a static-electric charge can easily be built up on a metallic member having a surface at the exterior of the housing.